/* * Directory notifications for Linux. * * Copyright (C) 2000,2001,2002 Stephen Rothwell * * This program is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License as published by the * Free Software Foundation; either version 2, or (at your option) any * later version. * * This program is distributed in the hope that it will be useful, but * WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * General Public License for more details. */ #include <linux/fs.h> #include <linux/module.h> #include <linux/sched.h> #include <linux/dnotify.h> #include <linux/init.h> #include <linux/spinlock.h> #include <linux/slab.h> #include <linux/fdtable.h> int dir_notify_enable __read_mostly = 1; static struct kmem_cache *dn_cache __read_mostly; static void redo_inode_mask(struct inode *inode) { unsigned long new_mask; struct dnotify_struct *dn; new_mask = 0; for (dn = inode->i_dnotify; dn != NULL; dn = dn->dn_next) new_mask |= dn->dn_mask & ~DN_MULTISHOT; inode->i_dnotify_mask = new_mask; } void dnotify_flush(struct file *filp, fl_owner_t id) { struct dnotify_struct *dn; struct dnotify_struct **prev; struct inode *inode; inode = filp->f_path.dentry->d_inode; if (!S_ISDIR(inode->i_mode)) return; spin_lock(&inode->i_lock); prev = &inode->i_dnotify; while ((dn = *prev) != NULL) { if ((dn->dn_owner == id) && (dn->dn_filp == filp)) { *prev = dn->dn_next; redo_inode_mask(inode); kmem_cache_free(dn_cache, dn); break; } prev = &dn->dn_next; } spin_unlock(&inode->i_lock); } int fcntl_dirnotify(int fd, struct file *filp, unsigned long arg) { struct dnotify_struct *dn; struct dnotify_struct *odn; struct dnotify_struct **prev; struct inode *inode; fl_owner_t id = current->files; struct file *f; int error = 0; if ((arg & ~DN_MULTISHOT) == 0) { dnotify_flush(filp, id); return 0; } if (!dir_notify_enable) return -EINVAL; inode = filp->f_path.dentry->d_inode; if (!S_ISDIR(inode->i_mode)) return -ENOTDIR; dn = kmem_cache_alloc(dn_cache, GFP_KERNEL); if (dn == NULL) return -ENOMEM; spin_lock(&inode->i_lock); prev = &inode->i_dnotify; while ((odn = *prev) != NULL) { if ((odn->dn_owner == id) && (odn->dn_filp == filp)) { odn->dn_fd = fd; odn->dn_mask |= arg; inode->i_dnotify_mask |= arg & ~DN_MULTISHOT; goto out_free; } prev = &odn->dn_next; } rcu_read_lock(); f = fcheck(fd); rcu_read_unlock(); /* we'd lost the race with close(), sod off silently */ /* note that inode->i_lock prevents reordering problems * between accesses to descriptor table and ->i_dnotify */ if (f != filp) goto out_free; error = __f_setown(filp, task_pid(current), PIDTYPE_PID, 0); if (error) goto out_free; dn->dn_mask = arg; dn->dn_fd = fd; dn->dn_filp = filp; dn->dn_owner = id; inode->i_dnotify_mask |= arg & ~DN_MULTISHOT; dn->dn_next = inode->i_dnotify; inode->i_dnotify = dn; spin_unlock(&inode->i_lock); if (filp->f_op && filp->f_op->dir_notify) return filp->f_op->dir_notify(filp, arg); return 0; out_free: spin_unlock(&inode->i_lock); kmem_cache_free(dn_cache, dn); return error; } void __inode_dir_notify(struct inode *inode, unsigned long event) { struct dnotify_struct * dn; struct dnotify_struct **prev; struct fown_struct * fown; int changed = 0; spin_lock(&inode->i_lock); prev = &inode->i_dnotify; while ((dn = *prev) != NULL) { if ((dn->dn_mask & event) == 0) { prev = &dn->dn_next; continue; } fown = &dn->dn_filp->f_owner; send_sigio(fown, dn->dn_fd, POLL_MSG); if (dn->dn_mask & DN_MULTISHOT) prev = &dn->dn_next; else { *prev = dn->dn_next; changed = 1; kmem_cache_free(dn_cache, dn); } } if (changed) redo_inode_mask(inode); spin_unlock(&inode->i_lock); } EXPORT_SYMBOL(__inode_dir_notify); /* * This is hopelessly wrong, but unfixable without API changes. At * least it doesn't oops the kernel... * * To safely access ->d_parent we need to keep d_move away from it. Use the * dentry's d_lock for this. */ void dnotify_parent(struct dentry *dentry, unsigned long event) { struct dentry *parent; if (!dir_notify_enable) return; spin_lock(&dentry->d_lock); parent = dentry->d_parent; if (parent->d_inode->i_dnotify_mask & event) { dget(parent); spin_unlock(&dentry->d_lock); __inode_dir_notify(parent->d_inode, event); dput(parent); } else { spin_unlock(&dentry->d_lock); } } EXPORT_SYMBOL_GPL(dnotify_parent); static int __init dnotify_init(void) { dn_cache = kmem_cache_create("dnotify_cache", sizeof(struct dnotify_struct), 0, SLAB_PANIC, NULL); return 0; } module_init(dnotify_init)